India plans to open 18 new embassies in Africa, Prime Minister Narendra Modi has said, in the latest sign that the Asian state is seeking to strengthen its presence on the continent.

Mr Modi made the announcement during a speech in the Ugandan parliament - the first by a serving Indian prime minister.

India currently has 29 full diplomatic missions in Africa, AFP news agency quotes officials as saying.

Mr Modi welcomed President Yoweri Museveni's policy of encouraging Ugandan Asians to return following the expulsion of many of them during the rule of Idi Amin in the 1970s.

"Our people are among the many threads that connect Uganda and India together," Mr Modi said.

"Your visionary leadership has enabled Ugandan people of Indian origin to return to their cherished home, regain their lives and help rebuild the nation that they deeply love," he told Mr Museveni.

India will boost its investments in Africa, and will keep its markets open to African states to "make it easier and more attractive to trade with India", Mr Modi said.

He added that more than 6,000 Indians serve in UN peacekeeping missions in Africa. More than 160 of them have died in the line of duty, the highest number for any country, Mr Modi said.

"India will work for you and with you; we will stand with you in your endeavours. We will speak for you and with you," Mr Modi added.

He said two-thirds of Indians and Ugandans was under the age of 35, and "if the future belongs to the youth then this is the time to build".

Mr Modi also unveiled plans to build a culture centre, named after India's anti-colonial campaigner Mahatma Gandhi, in Uganda's eastern town of Jinga, at the source of the River Nile.

Uganda's parliament tweeted details of the speech, including the scene as the special session drew to a close.